The use of modular link conveyors in industry enjoys increasing popularity. Particularly for conveying food articles or consumer products, especially in packages or in semi-packaged form, the modular link conveyor represents the overwhelming choice of those in the industry looking for a long-lasting, low cost conveying solution. In the recent past, significant advances in the development of such have been made so as to provide more efficient handling of an even larger variety of food articles, packages and containers, as well as other types of articles and products.
One of the most popular types of modular link conveyor systems on the market today, if not the most popular, is manufactured and sold by the assignee of the present invention under THE DESIGNER SYSTEM and WHISPERTRAX trademarks, and illustrated and claimed in prior U.S. Pat. No. 4,953,693, Sep. 4, 1990 and U.S. Pat. No. 5,031,757, issued Jul. 16, 1991 (the disclosures of which are fully incorporated herein by reference). Since the time of these early patents in the art, the significant advances have been fast in coming to provide an even more efficient operation and better handling and transporting of articles and products.
Despite eliminating the deleterious catenary approach prevalent in the prior art and the secure holding provided along the sides by the guide links, a problem sometimes arises with sagging of the conveyor chain in the vertical direction along the return run. This sagging is especially prevalent when a particular width of modular link chain is reached or exceeded. For example, in the case of a modular link chain with links styled similar to those shown in the '693 patent and with a four millimeter diameter stainless steel connector rod, the cutoff width is about twenty-five inches or more. Increasing the diameter of the connector rod is not an option without redesigning the corresponding link (which would then preclude retrofitting).
To prevent sagging of the chain intermediate of the sides, the solution practiced for many years is to support the chain externally along the return run of the endless conveying path. In the past, such support has been provided by structures such as curved rails spanning in the longitudinal direction (see, e.g., U.S. Pat. No. 5,190,145 to Ledginham et al.). These structures contact the conveying surface along the return run and thus provide the desired intermediate support.
The problems encountered with this arrangement are manifold. One is that, over time, the constant contact between the conveying surface and the external longitudinal rail along the return run tends to result in excessive wear. In particular, the longitudinal rail may over time create a groove or channel in the conveying surface of the belt or chain. Besides contributing to premature wear and potential failure, articles conveyed on the belt or chain can become unstable or caught on this groove or channel, either of which is deleterious for obvious reasons. Moreover, the groove or channel in some instances creates a deep crevasse that can be difficult to clean, and thus may serve as a breeding ground for bacteria or the like (a significant concern when food products or the like are being conveyed). While it is possible to rebuild the chain by removing the offending links, this represents a considerable undertaking in terms of expense and man hours.
Another problem is that this arrangement requires an uninterrupted path along the conveying surface of the chain for engaging the support. Thus, it cannot be used with chains having scoops, cleats, or other structures projecting from the conveying surface. A related problem is the requirement for external brackets for supporting the guide rail from the side frame, which can be awkward and in some cases may interfere with the smooth passage of the chain along the return run.
Accordingly, a need is identified for an improved arrangement for supporting a conveyor belt or chain along the return run of an endless conveyor. The arrangement would have particular utility in arrangements in which the belt or chain is particularly wide and thus susceptible to sagging intermediate of the side edges in the absence of external support. The usefulness would remain even in situations where a non-smooth conveying surface is provided.